$99 Cheap United flights Denver (DEN) to St. Louis (STL)

Scoring cheap one-way United Airlines flights from DEN to STL from $99 on Expedia couldn’t be simpler — just filter by “Price (lowest to highest).” Alternatively, check out our budget-friendly round-trip fares from $197 for your next exciting adventure.**These prices were available on Expedia within the past 7 days, for flights departing within the next year. Prices and availability are subject to change. Additional terms apply.

Search for return or one-way flights to St. Louis in January or February. You could find an affordable fare with United Airlines during these off-peak months.

Search for affordable United Airlines flights from Denver Intl. Airport (DEN) to Lambert-St. Louis Intl. Airport (STL) one to three months prior to your departure day. Travelers who book domestic flights 34 to 86 days in advance can save 25% compared to those who book just 6 to 12 days ahead. Regardless of fare type and itinerary, the ideal day to book a domestic flight is usually Sunday and the most expensive tends to be Monday. Passengers who book on a Sunday can save 6% on average compared to those who book their travel on a Monday.**Ideal booking window recommendation is based on average round-trip ticket prices for January through November for 2024. Best day of the week to book recommendation is based on average round-trip ticket prices for January through October 2024. All data sourced from ARC’s global airline sales database.

United Airlines has direct flights from Denver Intl. Airport (DEN) to Lambert-St. Louis Intl. Airport (STL), with 21 weekly departures. Simply choose the “Nonstop” and “Airline” filters while searching on Expedia to show all direct United Airlines flights to STL.

Leave Denver Intl. Airport (DEN) for Lambert-St. Louis Intl. Airport (STL) on a direct United Airlines flight, and you’ll be in the skies for about 2h 6m.

If it’s flexibility you’re after, Saturday offers the most choice for United Airlines flights from Denver Intl. Airport (DEN) to Lambert-St. Louis Intl. Airport (STL). You can pick from 3 different departures.

Taking off from DEN at 9:40AM UTC-7, the first United Airlines flight to STL lands at 12:48PM UTC-6. Traveling early means you’re less likely to encounter cancellations or delays.* Prefer a later start? The last United Airlines flight from DEN to STL departs at 5:37PM UTC-7 and touches down at 8:43PM UTC-6.*Most reliable time of the day recommendation is based on January through August 2024 flight status data sourced from OAG’s global flight data platform.

Hop on a United Airlines flight from Denver Intl. Airport (DEN) to St. Louis, and you’ll most likely land at Lambert-St. Louis Intl. Airport (STL). This is the airline’s primary hub in this destination.

A rewarding loyalty program and the chance to rack up points through United Mileage Plus are the start of the reasons to depart from DEN to STL with United Airlines. Plus, when you join our One Key™ program, you can receive OneKeyCash™* in addition to any airline loyalty program earnings. It’s yours to use wherever your next trip takes you.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.

You’ll likely be onboard an Airbus A319 or an Airbus A320 when flying United Airlines from Denver Intl. Airport (DEN) to Lambert-St. Louis Intl. Airport (STL). However, keep in mind that a different plane may be used due to operational demands.

Depending on the type of fare you purchased, a fee generally applies if you cancel or reschedule your flight more than 24 hours after it’s been confirmed. To secure plane tickets with more flexibility, select our “Changes included” or “No cancel fee” filter when you search for flights. For more information on canceling or changing your reservation, go to “Trips,” select your flight and click on “Manage Booking.”